1. Field of the Invention
The present invention relates to a sealing apparatus used in a shaft sealing section of various devices and appliances, particularly a sealing apparatus provided with a sealing lip made of a rubber-like elastic material and a sealing lip made of a resin.
2. Description of the Related Art
A conventional sealing apparatus of this type comprises a metal ring having a cylindrical portion and an inward flange portion folded from the open-air side end of this cylindrical portion radially inward, a first sealing member, made of a rubber-like elastic material, formed integral with the metal ring, and a second sealing member, made of a resin material, held between the inward flange portion of the metal ring and the first sealing member. The first sealing member has a first sealing lip which extends to the axial direction sealing liquid side and has a lip leading end slidably in sealing contact with the surface of a rotary member. The second sealing member has a second sealing lip which is located in a gap between the open-air side surface of the first sealing lip and the rotary member and has an inner periphery slidably in sealing contact with the surface of the rotary member.
The second sealing lip made of resin supports the first sealing lip, and inhibits an excessive deformation of the first sealing lip when pressure of the sealing liquid becomes excessively high. Double sealing is ensured by the first sealing lip and the second sealing lip by causing the inner periphery of the second sealing lip to come into sealing contact with the rotary member.
In the conventional art as described above, however, the first sealing lip made of rubber is easily susceptible to wear, and cannot sufficiently prevent leakage of the sealing liquid.
Leakage of the liquid having leaked from the first sealing lip on the open air side is prevent to some extent by the second sealing lip of resin. However, the main role of the second sealing ring made of resin is to inhibit deformation of the first sealing lip made of rubber, resulting in an insufficient sealing property.
The second sealing lip made of resin, requiring rigidity to some extent with a view to fully causing it to display the deformation inhibiting function of the first sealing lip, is poor in flexibility and has only an insufficient follow-up property relative to axial eccentricity of the rotary member.
Since the first sealing lip has a foot shape which permits only drawing a curvature simply from the radial direction to the axial direction, the bend at the foot of the second sealing lip made of resin bending along such a curvature has only a small degree of freedom of bending.
This causes an increase in tension with the rotary member upon occurrence of axial eccentricity, accelerating wear, and produced wear powder of the resin causes deposition of sludge. This forms a cause of occurrence of liquid leakage from interruptions of the lip line of the second sealing lip made of resin.
The deformation inhibiting function of the first sealing lip provided by the second sealing lip made of resin is limited to a certain extent, and deformation of the first sealing lip under a high sealing liquid pressure cannot sufficiently be inhibited.